simulation of a brushless direct current motor based on finite state machine theory

A novel method simulating a brushless direct current(DC) motor was presented, based on principles of hybrid system modeling and finite state machine theory. Brushless DC motor control mainly focuses on controlling the on/off condition and power switch duration. Modes of control therefore can be defined by corresponding states, and the states can be combined as a finite state machine. This approach uses the popular Simulink/Stateflow simulation method to control brushless DC motor loops. A three phase brushless DC motor was analyzed to illustrate the process of model building with Simulink/Stateflow. The analysis demonstrates the feasibility and validity of the proposed method.     

Analysis of operating characteristics of dual stator-winding wind power induction generator

To research the operating characteristics of dual stator-winding induction generator(DWIG) in wind power generation system,the operating mechanism and features of DWIG with the speed change as well as the load change are analyzed based on the equivalent circuit and phasor diagram. And then,the calculation methods of control winding current with different loads are derived. Furthermore,aiming at the rated and variable speed operation modes,the operating characteristics of a 18.5 kW DWIG with inductive load are analyzed in detail. The results show that the control winding can regulate the excitation reactive power to build up the no-load voltage. With the increase of the load current,the control winding current and the slip ration increase,and the efficiency increases first and then decreases. The control winding can regulate the reactive power in variable speed condition for constant voltage output. The correctness of the research is verified by the consistency of the theoretical analysis and the simulation results.     

小麦旗叶衰老过程不同数学模型拟合比较及衰老特征分析

为了准确了解小麦叶片的衰老特征,筛选适合描述小麦叶片衰老过程的数学模型, 2011年和2012年分别以91个和105个小麦品种(系)为材料,用S型曲线中的Logistic、Gompertz和Richards模型拟合了试验品种叶片的衰老过程,解析了其叶片衰老特征。结果表明,试验品种可分为延绿、中等延绿、中等早衰和早衰4种类型。其旗叶衰老过程可分为衰老起始期、快速衰老期和衰老结束期3个阶段,3个阶段旗叶的衰老速度表现为慢–快–慢,不同延绿类型品种开花后旗叶的绿色叶面积百分比下降主要在衰老过程的中后期。3种模型对不同延绿类型品种旗叶衰老过程均可以拟合,Gompertz和Richards模型拟合度接近,高于Logistic模型。Gompertz模型的拟合度以早衰中等早衰中等延绿延绿类型。不同延绿类型品种旗叶衰老曲线特征参数达到最大衰老速度时间(TMRS)、平均衰老速度(ARS)和绿色叶面积持续期(GLAD)存在显著差异, TMRS和GLAD以延绿中等延绿中等早衰早衰, ARS以早衰中等早衰中等延绿延绿。Gompertz模型对小麦叶片衰老过程的拟合度优于Logistic模型。叶片衰老过程特征参数可以用于品种延绿性差异评价。     

Accurate mathematical models for relief grinding of gear hob cutters

A mathematical model for accurate relief grinding of gear hob cutters along radial directions is presented based on the analysis of grinding geometry. Both the design and manufacturing models of gear hob cutters are carefully derived and presented. By employing the plane envelope theory, the reference contour of the grinding wheel is determined in order to attain the design tool profile precisely. The tooth profile error model after regrinding is also given to confirm the grinding parameters. The model provides accurate solutions for both the tool profile and the sectional contour of the grinding wheel. It is simple and straightforward and can be used to produce high precision hob cutters systematically. Two numerical examples are presented to illustrate the effectiveness of the proposed method. The model computing results indicate that the proposed method is practical, precise and reliable. The method provides valuable reference for the design and machining of hob cutters.     

三边形桅杆风荷载谱模型试验研究

对三边形格构式桅杆进行了均匀流和两种紊流下的高频测力天平风洞试验,得到了顺风向、横风向和扭转向的气动力系数以及脉动风荷载谱。采用基于风速谱的数学模型对顺风向脉动风荷载谱进行拟合,验证了该经验公式在不同流场下的适用性。根据试验所得横风向和扭转向脉动风荷载功率谱曲线的特点,建立由紊流激励和旋涡脱落激励两部分组成的谱函数数学模型,最小二乘法拟合结果与风洞试验结果吻合良好。横风向脉动风荷载谱以紊流激励为主,紊流强度15%时旋涡脱落激励贡献仅占10%,扭转向脉动风荷载谱中旋涡脱落激励贡献明显增大,达到40%。     

Dynamic characteristics of multi-stage planetary gear trains in shield machine cutter drive

A purely torsional dynamic model of multi-stage planetary gear trains is developed to investigate the dynamic characteristics of the transmission system in shield machine cutter drive. In the model,phase difference between mesh stiffness and error among each stage caused by different initial mesh positions is considered,and other factors such as component bearing stiffness,time-varying mesh stiffness and error are considered as well. Inherent characteristic analysis shows there are more unique and diverse vibration modes in multi-stage planetary gear trains than in single-stage planetary gear trains. Through dynamic response analysis,time-domain and frequency-domain response of dynamic meshing force of each stage is obtained. As the frequency of exciting force of medium-speed and high-speed stage is in proximity to the natural frequency of the system,harmonic resonance tends to occur,which needs to be paid great attention to. Dynamic factors of each stage are also computed and prepare the ground for the dynamic optimizing design of planetary gear trains.     

Analysis on the export characteristics and internal flow of circumferential micro-turbines

Circumferential micro-turbine adapts to miniaturization as it has simple structure. To evaluate and improve the six-blade micro-turbine structure and analyze the influence of tip clearance on the flow, To simulate the output characteristics and gas flow characteristics, a three-dimensional transient numerical simulation model is set up and the output characteristics and gas flow characteristics are simulated. Results show that the six-blade turbine has structural defect. Parts of gas directly exhaust without working because intake port and exhaust have periodic connectivity while running. Simulation results for the improved eight-blade micro-turbine reveal that it hasnt such defects. Then, the effect to pressure drop of tip gap is simulated, and results show that the influence is nonlinear. As the gap is less than 0.01, the pressure drop is very sensitive to the gap. When gap is greater than 0.02, its impact is very small. Simulation and experimental results both show that the output mechanical power of the eight-blade turbine and six-blade turbine increases with the increase of gas flow. The eight-blade turbine mechanical power is 1 355 mW, which is increased 10.5% over the six-blade turbine. The power output start flow of eight-blade turbine is 140 L/h, while that of six-blade turbine is 200L/h. The performance of eight-blade turbine is better than that of six-blade turbine.     

发动机用平板型空滤器流动阻力特性分析和改进

为减小平板型空滤器流动阻力以增大进气量,对平板型空滤器流动阻力特性开展了实验研究,获得了空滤器流动阻力随流量变化的规律和阻力构成成分。阻力随流量的增大而加速增大,滤芯阻力约占整个空滤器阻力的一半,入口流量为120 m 3/h时,总阻力为915.3 Pa,滤芯阻力为426.4 Pa。在实验获得滤芯阻力参数的基础上,提出采用多孔介质跃升模型对平板型空滤器内部流场开展三维数值仿真分析,结果表明,仿真结果与实验结果比较吻合,最大误差为5.67%。滤芯阻力同样约占整个阻力的一半,另一半阻力主要为出口处阻力,其余壁面阻力约占15%。最后,在实验和仿真分析的基础上,提出了改进模型并进行了仿真分析。结果表明,改进模型阻力有较大程度的下降,入口流量为120 m 3/h时,总阻力为588.2 Pa,较原始模型下降了32.2%;增大空滤器流通横截面积是减小阻力以增大进气量的有效手段,改进空滤器壁面的平滑性是补充措施。     

玉米杂交种产量性状与穗位叶光合性状关联度分析

玉米的产量是由多个因素共同作用的结果,果穗产量性状是其直接表现。玉米植株中部叶片尤其是穗位叶的光合性状对籽粒产量的形成具有重要作用。因此,分析玉米穗位叶光合性状与玉米杂交种产量性状间的相互关系对选育高产、优质、抗病、广适玉米新杂交种具有重要意义。此文应用灰色关联度分析方法,对玉米杂交种穗部产量性状与穗位光合性状间的相关性进行了分析。结果表明：与玉米杂交种单穗粒重最为相关的穗部光合性状是穗位茎节长,其次是叶面积、叶长、光合效率和比叶重等。对玉米杂交种穗部产量性状综合影响较大的穗位光合性状有穗位茎节长、叶长、比叶重等。     

西安市降雨特征的多尺度分析

为对西安市不同等级降雨特征及未来演变趋势进行研究,采用线性回归、Mann-Kendall 检验、R/S 分析和ARIMA模型等方法分析1951—2013 年降雨量（日）资料。结果表明：（1）小雨、中雨、大雨及以上和总降雨量均表现出减少趋势,倾向率分别为-7.3、-2.6、-3.0、-13.6 mm/10 a,多在20 世纪60—70 年代出现减少的突变（除中雨外）。（2）小雨和总降雨日表现出减少趋势,倾向率分别为-3.3、-3.6 d/10 a,均在20 世纪80 年代后期出现减少的突变,90 年代后期后减少趋势达到显著性水平。大雨及以上等级降雨日表现出阶段性增加和减少的特点。（3）R/S 分析法和Hurst 指数试验（包括20 年试验和累加试验）分析均表明,除中雨外,未来西安市小雨、大雨及以上和总降雨量（日）将持续减少。未来西安市不同等级降雨量（日）继续减少的持续性强度为小雨量（日）＞总降雨量（日）＞大雨量（日）,Hurst 指数序列图可用于突变点或显著变化点的检测。ARIMA模型在短期内预测精度仍较高[降雨量（日）的预报相对误差低于20%],可以用于降雨量（日）的气候预测。     

Analysis of plastic flow characteristics based on bridge steel 16Mn ratcheting

Abstract:The analysis of the plastic flow characteristics on the basis of the ratcheting experimental results for the bridge steel 16Mn are carried out by calculatig the plastic modulus H and the angle θ between the backstress rate deviator and the plastic flowdirection. The different mechanisms causing uniaxial andmultiaxial non proportional ratchetting are illustrated, that is, the starting and evolution of uniaxial ratchetting is due to the different values of the plastic modulus H at the symmetric loading points with respect to the mean stress. On the other hand, the staring and evolution of multiaxial non proportional ratcheting is driven by H and θ variations. The influence of loading history on ratchetting is the result of the influence of loading history on the angle θ.     

利用频域有限元法分析内嵌管式辐射地板频域热特性

分析内嵌管式辐射地板的频域热特性,便于进一步了解内嵌管式辐射地板的动态热特征,为辐射地板的系统和控制设计提供重要的参考依据。建立了内嵌管式辐射地板的频域有限元模型,同时采用ANSYS软件建立了内嵌管式辐射地板的时域传热模型,通过2个模型的对比说明了频域有限元模型的准确性。采用频域有限元模型计算并分析了内嵌管式辐射地板的频域热特性。结果表明,在低频区域,地板的频域热响应基本不随频率变化,其传热过程接近于稳态,而在高频区域,地板的频域热响应随频率的变化十分剧烈,地板传热呈现明显的动态特征。当房间内存在较多成分的高频热扰时,关于辐射地板的传热计算应采用动态计算方法。     

Analysis on denitrification characteristics of an aerobic denitrifier in the system of SUFR-UCT

An aerobic denitrifier Y4 is isolated from the activated sludge of UCT system’s aerobic reactor, which is identified as Gordonia.sp according to the 16S rDNA similarity comparison and analysis. The study on denitrification capability of strain Y4 shows that strain Y4 could effectively remove the nitrate nitrogen in the culture under aerobic conditions, and the nitrogen removal efficiency within 48 hours up to 61.2% when the initial concentration of nitrate nitrogen is 286 mg/L. Another test investigated the effects of denitrification on DO and temperature, the results show that strain Y4 has a high oxygen tolerance. When the DO is 2~11.8 mg/L, the denitrification rate could be maintained at a high level. Strain Y4 also has a high temperature adaptation, the denitrifying rates is up to 90% at 30 ℃. The tests prove that there is aerobic denitrifier which has good performance of aerobic denitrification in the SUFR-UCT system.     

Kinematic and dynamic analysis and simulation on parallel kinematics machine tool

The parallel kinematics machine tool is based on the space of mechanism. It can achieve space complex motion, meet requirements of processing of multi-degree freedom, and can process complex parts. Because the design process of a parallel kinematics machine tool is quite complicated, there are limitations of the traditional design methods using experience and static researches. It is necessary to explore the related design theories and study the dynamic characteristics of the parallel kinematics machine tool. This study takes a 4-XPXUYYUX parallel kinematics machine tool as an example, develops the mathematical model of kinematics analysis by the coefficient method. The dynamic model is solved using Lagrange equation, which can provide the basis for other theoretical analysis. We develop a simulation model of parallel kinematics machine tool by the virtual prototype software-ADAMS, and analyze the dynamic of parallel kinematics machine tool. The dynamic characteristics of parallel kinematics machine tool are acquired. The system design of parallel kinematics machine tool is improved and optimized.     

不同海拔初烤烟叶主要烟气指标特征分析

为了探讨云南优质烟区不同植烟海拔高度初烤烟叶卷烟烟气特征,以云南省主栽烤烟品种之一K326品种为试材,通过对不同海拔(1200-2000m)烟区初烤烟叶烟气焦油量及其他主要烟气指标值的分析显示,不同海拔高度初烤烟叶卷烟烟气的焦油量、烟碱含量及一氧化碳含量等主要指标值 有很大差异。以200m为一个递增单位,海拔从1200m上升到1800m,焦油量、烟碱量、一氧化碳量及总粒相物值总体上呈降低趋势,在海拔1800m处达最低值,随海拔继续升高到2000m,四项指标值均随之增加,但最终均未达到1600m处水平。同处1800m海拔,田烟较山地烟的焦油量、烟气烟碱、总粒相物及一氧化碳量高。因此,海拔在1800m烟区的初烤烟叶,尤其是来自于山地烤烟的初烤烟叶的卷烟各指标值对高档卷烟配方的工业可用性更好。     

安宁河流域主要种植模式生态经济效益分析

通过对安宁河中游地区作物主要种植模式的调查,并将收集的调查数据进行技术经济和生态效益分析,从中找出较为合理的农作物种植模式,以便为当地农业生产中的作物选择和作物间的相互结合提供理论指导,以利进一步提高当地作物生产水平,提高自然资源的利用率。1调查方法和内容1.1调查基本情况调查于2002年6月上旬在安宁河中游的西昌市西乡乡马坪坝村进行。首先将马坪坝村的所有农户进行随机抽样,然后分别对其田间作物种植情况进行实地调查并走访农户获取数据。马坪坝村地势较平坦,土壤肥沃,水热条件较好(干湿季节分明,一般6-10月为雨季,11月至翌…     

Establishment and analysis of dynamic mathematical model for coal gasifier

Based on the analysis of flowing combustion, gasification reaction, and lumped parameter, a three region model is established to predict the temperature and gas components of Texaco coal gasifier. Using mass balance and energy balance equations to each zone, the model takes account of gas solid two phase flow, coal pyrolysis, radiation heat transfer, and heterogeneous and homogeneous kinetic chemical reactions. Based on the model, a program is developed for dynamic and static simulation. After parameterization and simulation analysis, some important trends and conclusions are attained. Because the model can accurately predict the temperature and gas components in jet region, it has widespread engineering application value.     

Analysis of vibrating characteristics of multi-span continuous skew bridges

To explore the vibrating frequencies and rational impact factors of multi-span skew bridge, the recursive algorithm of vibrating frequency and finite element formulations of static and dynamic analysis are established for uniform section multi-span continuous skew bridge. The first five order frequency changes of equal-span multi-span continuous skew bridge and unequal-span multi-span skew bridge are compared. The interaction of vehicle-bridge system for two-span skew bridge is analyzed. The history curves for deflection and moment of middle-span are presented. The influence of obliquity on dynamic deflection and dynamic moment as well as the influence of vehicle velocity and obliquity on impact factors of deflection and moment are investigated. Results show that the fundamental frequency of multi-span skew bridge is identical to that of single span skew bridge. The higher order frequencies of single span skew bridge are distributed in frequencies of multi-span skew bridge, which mix other vibrating frequencies. The more the span number is, the more the other vibrating frequencies mingle. Obliquity has an important influence on dynamical characteristics of skew bridge. Impact effects of vehicle have no harmonious changing rule with vehicle velocity and obliquity. The impact factors of deflection and moment are different for skew bridge.     

内框架箱型混凝土结构施工活荷载实测分析

施工期早龄期钢筋混凝土结构与模板支撑系统组成临时承载体系为时变结构,其承担的荷载主要有新浇筑混凝土自重与包括施工人员和设备荷载以及混凝土浇筑时产生的冲击和振捣荷载在内的施工活荷载。将多层连续施工时变结构体系模拟成一组弹性支撑连续板,根据该模型分析了施工期现浇钢筋混凝土结构的受力特性。根据现场实测数据,以构件有效承载面积为统计对象,计算了混凝土施工荷载的统计参量,并参考相关研究成果,以95%的置信度对施工期活荷载标准值进行反演,建议施工活荷载标准值取2.5 kN/m 2。     

电脑在种子生产、经营与管理中的应用

以电脑和网络为基础的知识经济时代已经到来,电脑和网络技术也进入了作物种子生产、经营与管理领域。早在20世纪70年代,为了适应种子工作的需要,一些发达国家如美国、俄罗斯、日本等就实现了品种资源档案的电脑管理。1984年,新西兰将电脑用于种子检验工作,从样品接收、登记、测定数据处理、种子分级到结果报告、种子证书签发、检验费用计算等全部用电脑处理。1988年,美国将电脑用于种子加工,设计了种子清选的电脑控制系统,可对混入作物种子中的其它植物种子进行有效的分离。现在,电脑技术已全面进入发达国家的作物种子经营与管理领域。种子…